1. Field of the Invention
The invention generally relates to a transistor and a fabrication method thereof, and more particularly to a transistor having an oxide semiconductor channel layer and a fabrication method thereof.
2. Description of Related Art
Recently, as compared to traditional amorphous silicon (a-Si) thin film transistor, since oxide semiconductor thin film transistor encompasses a higher carrier mobility and a more stable threshold voltage (Vth) while being suitable for large area fabrication, it is widely used in display panels gradually.
In general, there are three types of commonly seen oxide semiconductor thin film transistors (TFTs) including Coplanar TFTs, Island Stop/Etch Stop layer (IS/ESL) TFTs, and Back Channel Etch (BCE) TFTs. Among these, the BCE and IS/ESL type oxide semiconductor thin film transistors have advantages in device characteristics and fabrication yield. Moreover, as compared to IS/ESL TFTs, the BCE TFTs can further save one photolithography and etch process (PEP), and thus has an even better advantage.
However, in the fabrication process of the BCE type oxide semiconductor thin film transistors, a photoresist used for patterning a channel layer would be directly in contact with the channel layer. In addition, the photoresist includes organic solvent which would affect the Subthreshold Swing (SS) of the transistors. As a result, the electrical properties and stability of the transistors are compromised.